Sen. John McCain said Wednesday he is working on an amendment that would add an Afghanistan strategy to the annual defense policy bill, after complaining that the Trump administration has yet to develop any new approaches to America's longest running conflict.

The Arizona Republican has criticized the administration for weeks over its lack of a new strategy and threatened to force one on the Pentagon. He said he will now propose a strategy created by his Armed Services Committee as part of the National Defense Authorization Act, which is now awaiting a floor vote.

"I told them months ago, unless you give us a strategy, we'll give you a strategy," McCain said.

Defense Secretary Jim Mattis admitted the U.S. is not winning in Afghanistan during testimony in June, and promised McCain and the committee a new strategy was coming by mid-July.

When asked about troop numbers in Afghanistan Tuesday, Mattis said, "I'm still putting together my ideas on that." Mattis has said he is working to put together a more regional strategy and is consulting with the president.

President Trump has delegated more authority to Mattis to decide how many additional troops should be added to the 8,400 currently deployed to Afghanistan.

The administration is reportedly considering an increase of 3,000 to 5,000 troops, though Mattis has declined to confirm any range of new deployments.